| 1 | GU | AVIATECA, S.A. | ICAO: GUG, IATA Prefix: 240, Subsidiary of Grupo TACA. Name changed to Avianca Guatemala | GCA | AVCODES |
| 2 | GU | Empresa Guatemalteca de Aviacion (AVIATECA) | ICAO: GUG, IATA Prefix: 240, | GCA | AVCODES |
| 3 | GU | (G&U) Grafton & Upton R.R. Co. | 4/1970-7/2000; eliminated 1/2003; 7/2005 | | NAKINA |
| 4 | GU | (G&U) Grafton & Upton R.R. Co. | 4/70-7/2000 | | NRHS |
| 5 | GU | GRAFTON & UPTON RAILROAD COMPANY | | | PWRC |
| 6 | GU | Grafton and Upton Railroad | | | RSRV |
| 7 | GU | GRAFTON AND UPTON RAILROAD COMPANY | | | SCAC4 |
| 8 | GU | Grafton and Upton Railroad | | USA | TRAFFIC |
| 9 | GUA | Aerotaxis de Aguascalientes, S.A. de C.V. | Callsign: Aguascalientes, | MEX | AVCODES |
| 10 | GUA | Aerotaxis de Aguascalientes | | | ICAO1 |
| 11 | GUA | | City: Guadalajara | MEX | TRAFFIC |
| 12 | GUAAF | Guangxi Air Force | Guangxi Air Force was a regional air force established around 1932 by the New Guangxi Clique under leaders Li Zongren and Bai Chongxi, operating independently until integrating with the Chinese Nationalist air force in November 1937. | ROC | TRAFFIC |
| 13 | GUAD | GUARDIAN MOVING AND STORAGE | | | SCAC4 |
| 14 | GUAF | GUARANTEED AIR FREIGHT FORWARDING, INC | | | SCAC1 |
| 15 | GUAN | GUANGDONG ETERNAL WAY INTL FREIGHT | | | SCAC4 |
| 16 | GUANG | Guangzhou Metro | | PRC | TRAFFIC |
| 17 | GUAQ | GUARRIELLO TRUCKING LLC | | | SCAC4 |
| 18 | GUAV | GUAVA EXPRESS INC | | | SCAC4 |
| 19 | GUAX | Georgia Power Co. | added 10/1982; 1/1994; eliminated 10/1999; 7/2000 (not listed); added 10/2000; 7/2005 | | NAKINA |
| 20 | GUAX | Georgia Power Co. | added 10/82; 1/94; eliminated 10/99; 7/2000; added 10/2000 | | NRHS |
| 21 | GUAX | GEORGIA POWER COMPANY | | | PWRC |
| 22 | GUAX | Georgia Power | | | RSRV |
| 23 | GUAX | GEORGIA POWER COMPANY | | | SCAC4 |
| 24 | GUAY | GUAY, L P (1987) INC | | | SCAC4 |
| 25 | GUB | Gamla Uppsala Buss AB | City: Uppsala | S | TRAFFIC |
| 26 | GUBA | GARZA, UBALDO | | | SCAC4 |
| 27 | GUBE | GRUBE, BOB | | | SCAC4 |
| 28 | GUC | Puer General Aviation Co., Ltd. | IATA: R8, Callsign: Leaf Air, Designator R8 recalled by IATA | PRC | AVCODES |
| 29 | GUC | Puer General Aviation Co., Ltd. | Callsign: Leaf Air, Designator R8 recalled by IATA | PRC | AVCODES |
| 30 | GUCC | GULF ENERGY MARITIME (GEM) PJSC | | | SCAC4 |
| 31 | GUCG | GUNTHERS LOGISTICS LLC | | | SCAC4 |
| 32 | GUCI | GULF COAST INTERMODAL INC | | | SCAC4 |
| 33 | GUCK | GULICK TRUCKING INC | | | SCAC4 |
| 34 | GUDC | GREMIO UNIDO DE CHOFERES Y TRABAJAD | | | SCAC4 |
| 35 | GUDC | Gelligaer Urban District Council | | GB | TRAFFIC |
| 36 | GUDG | GUADALUPE DE GUAYMAS SPR DE RL | | | SCAC4 |
| 37 | GUDN | GUARIDIAN TRANSPORT LLC | | | SCAC4 |
| 38 | GUDQ | GUARANTEE DELIVERY SERVICE | | | SCAC4 |
| 39 | GUDR | GUILD OF AUTOMOTIVE RESTORERS, THE | | | SCAC4 |
| 40 | GUDU | GUD GESELLSCHAFT FUR UMWELDIENSTE M | | | SCAC4 |
| 41 | GUE | Aero Servicio Guerrero, S.A. de C.V. | Callsign: Aero Guerrero, | MEX | AVCODES |
| 42 | GUED | GUERRA CARDENAS, ARTURO | | | SCAC4 |
| 43 | GUEE | GULF EUROPE EXPRESS | | | PWRC |
| 44 | GUEI | GUERRA RODRIGUEZ, PABLO | | | SCAC4 |
| 45 | GUEQ | GTA-US EXPRESS INC | | | SCAC4 |
| 46 | GUEX | General American Marks Co. | added 1/1998; 7/2000-7/2005 | | NAKINA |
| 47 | GUEX | General American Transportation Corp. | added 4/1971; 1/1975-1/1994; eliminated 1/1998 | | NAKINA |
| 48 | GUEX | General American Transportation Corp. | added 4/71; 1/75-1/94; eliminated 1/98 | | NRHS |
| 49 | GUEX | General American Marks Co. | added 1/98; 7/2000 | | NRHS |
| 50 | GUEX | GENERAL AMERICAN MARKS CO. [GENERAL AMERICAN TRANSPORTATION CORP.] | | | PWRC |
| 51 | GUEX | General American Marks (GATX Corporation) | | | RSRV |
| 52 | GUF | Gulf African Airlines Limited | Callsign: Gulf African, | WAG | AVCODES |
| 53 | GUF | Gulf African Airlines - Gambia | | | ICAO1 |
| 54 | GUFM | GULF FLEET MANAGEMENT LLC | | | SCAC4 |
| 55 | GUG | AVIATECA, S.A. | IATA: GU, IATA Prefix: 240, Subsidiary of Grupo TACA. Name changed to Avianca Guatemala | GCA | AVCODES |
| 56 | GUG | Empresa Guatemalteca de Aviacion (AVIATECA) | IATA: GU, IATA Prefix: 240, | GCA | AVCODES |
| 57 | GUG | Aviateca | | | ICAO1 |
| 58 | GUGN | GLORY UNIVERSAL GROUP INC | | | SCAC4 |
| 59 | GUGT | GUGLIELMETTI TRUCKING LLC | | | SCAC4 |
| 60 | GUHB | GUTHRIE-HUBNER INCORPORATED | | | SCAC4 |
| 61 | GUIC | GUILES, CRAIG | | | SCAC4 |
| 62 | GUIE | GREENCORE USA INC | | | SCAC4 |
| 63 | GUIL | GUILFORD TRANSPORTATION INDUSTRIES, INC | | | PWRC |
| 64 | GUIN | GUINEY DELIVERY SERVICE INC | | | SCAC4 |
| 65 | GUIN | Guinness Tramway | | IRL | TRAFFIC |
| 66 | GUIR | GUIRO TRUCKING | | | SCAC4 |
| 67 | GUIS | GRACE UNIVERSAL INC | | | SCAC4 |
| 68 | GUIZ | GUNDERSON INDUSTRIES | | | PWRC |
| 69 | GUJ | Gujarat Airways Limited | IATA: G8, Callsign: Gujartair, IATA designator changed from G8* | IND | AVCODES |
| 70 | GUJ | Gujarat Airways Limited | IATA: G8, Callsign: Gujartair, IATA designator changed to G8 | IND | AVCODES |
| 71 | GUJ | Gujarat Airways | IATA: G8 | | ICAO1 |
| 72 | GUKI | GURU TRUCKING INC | | | SCAC4 |
| 73 | GUL | Gull Air | Callsign: Gull-Air, | USA | AVCODES |
| 74 | GUL | Gull Air | | | ICAO1 |
| 75 | GULA | GULF COAST ENERGY | | | SCAC4 |
| 76 | GULC | GUILDCREST TRANSPORTATION INC | | | SCAC4 |
| 77 | GULF | GUIGNARD FREIGHT LINES INC | | | PWRC |
| 78 | GULH | GAULT, L H & SON INC | | | SCAC4 |
| 79 | GULI | GULLY TRANSPORTATION, INC | | | SCAC1 |
| 80 | GULK | GULICK, KEVIN | | | SCAC4 |
| 81 | GULL | GULF TRANSPORT LLC | | | SCAC4 |
| 82 | GULT | GULFSIDE TRANSPORTATION INC | | | SCAC4 |
| 83 | GULV | GULF MOVING SYSTEMS | | | SCAC4 |
| 84 | GUM | Gum Air N.V. | Callsign: Gum Air, | SME | AVCODES |
| 85 | GUM | Gum Air | | | ICAO1 |
| 86 | GUMA | GULICK TRUCKING INC | | | SCAC4 |
| 87 | GUMM | GUINDON MOVING & STORAGE | | | SCAC4 |
| 88 | GUMO | GUINDON MOVING AND STORAGE | | | SCAC4 |
| 89 | GUMT | GUME TRANSPORT & STORAGE INC | | | SCAC4 |
| 90 | GUMV | GUM, V G & SON TRUCKING INC | | | SCAC4 |
| 91 | GUN | Grant Aviation, Inc. | IATA: GV, Designator GS* reinstated/changed by IATA | USA | AVCODES |
| 92 | GUN | Grant Aviation | IATA: GS | | ICAO1 |
| 93 | GUNB | GUNDLACH & SONS LEASING COMPANY INC | | | SCAC4 |
| 94 | GUND | GUNN, CLAUDE R | | | SCAC4 |
| 95 | GUNE | GUNTREN EXPRESS INC | | | SCAC4 |
| 96 | GUNG | GUNGEN DENIZCILIK VE TICARET A S | | | SCAC4 |
| 97 | GUNH | GUNTHERS TRANSPORT | | | SCAC4 |
| 98 | GUNI | GUNDI INC | | | SCAC4 |
| 99 | GUNN | GUNSON, R TRUCKING | | | SCAC4 |
| 100 | GUNS | GUNSON TRANSPORT | | | SCAC4 |
